Experimental Determination of Lipid Electropore Size

Abstract

Electroporation is a process by which nanometer-sized pores are formed in the plasma membrane by high-power electric pulses (EP). Electroporation has many applications, including the delivery of genes and drugs into cells, as well as tumor ablation. Understanding the nature of pores, including size and resealing properties, under various EP exposure conditions is essential for various applications of biomedicine and biotechnology. To better understand the properties of electropores, researchers have employed a variety of experimental approaches to determine electropore size. First, and perhaps the most widely used, is the fluorescent detection of membrane-impermeable markers, such as YO-PRO-1 (YP) and propidium (Pr) iodide, into the cell following EP treatment. Similarly, researchers can track the flow of small inorganic ions, such as thallium (Tl⁺), using fluorescent detection techniques. Because Tl⁺ is much smaller than either YP or Pr, comparing their relative uptake can provide a measure of the proportion of small versus large electropores in the membrane. A third, and arguably more accurate, approach involves the manipulation of cell volume changes following EP exposure. This approach allows one to estimate the upper limit of electropore size based on the molecular dimensions of solutes which block cell swelling. Finally, the pore selectivity and pore size can be analyzed by patch clamp. Combined, these approaches allow one to experimentally determine electropore size under different EP treatments.